The present invention relates to an arrangement for optical beam transformation, including at least one light source which can emit at least one light beam, with the at least one light beam having a greater divergence in a first direction than in a second direction at right angles to it, a collimation means, which can at least reduce the divergence of the at least one light beam in the first direction, an apparatus for optical beam transformation, which is arranged downstream from the collimation means in the propagation direction of the at least one light beam, with the apparatus being designed such that the divergence of the at least one light beam passing through the apparatus in the first direction is interchanged with the divergence in the second direction at right angles to it. The present invention also relates to an apparatus for optical beam transformation, having at least one inlet surface and at least one outlet surface, with the apparatus being designed such that the divergence of a light beam passing through the apparatus in the first direction is interchanged with the divergence in the second direction which is at right angles to it.
An arrangement as well as an apparatus of the type mentioned above are known from European Patent Application EP 1 006 382 A1. The apparatus described in this document has, for example, a substrate composed of a transparent material which has an inlet surface and an outlet surface. Both the inlet surface and the outlet surface are designed to be essentially rectangular and elongated. The longitudinal extent of the inlet surface and of the outlet surface corresponds essentially to the second direction. If a laser diode bar is used as the light source, this second direction corresponds to the direction in which individual emitters in the laser diode bar are arranged alongside one another and at a distance from one another. This direction of reduced divergence is referred to as the slow axis. The first direction, at right angles to it, is the direction of greater divergence, which in the case of semiconductor laser diode bars is referred to as the fast axis.
In the apparatus, which is known from the abovementioned art, two or more cylindrical lenses are provided both on the inlet surface and on the outlet surface, and their cylinder axes are all aligned parallel to one another. The cylinder axes of the cylindrical lenses on the inlet surface and on the outlet surface each include an angle of 45° or −45° both with the slow axis and the fast axis. A light beam which emerges from an emitting section of a laser diode bar and which in the end extends in the form of a line in the slow axis direction is rotated through 90° as it passes through the apparatus for optical beam transformation that is known from the prior art, so that the light beam is in the form of a line in the fast axis direction after passing through the apparatus. An apparatus such as this offers the advantage that the rotation of the individual light beams makes it harder for the individual light beams to overlap in the slow axis direction.
With this apparatus, which is known from the art, it has found to be disadvantageous that the cross section of the beam is enlarged overall as it passes through the apparatus, because the cylindrical lenses, which are all parallel to one another, influence the beam only in a direction at right angles to the propagation direction while, in contrast, the direction which is at right angles to this first direction is not influenced at all by the apparatus or by the cylindrical lenses in the apparatus. The beam therefore diverges in this direction, so that the individual beam elements which have passed through the apparatus can be focused only with comparative difficulty at a common focus point after having passed through the apparatus. This is due, inter alia, to the fact that an image of the individual emitters of the light source (which is, by way of example, in the form of a laser diode bar) is created downstream from the device in a direction which is at right angles to the propagation direction while, in contrast, this is not the case for the other direction, which is at right angles to the propagation direction and to the abovementioned direction. Furthermore, the widening of the beam while passing through the apparatus can lead to the individual beam elements at least partially overlapping so that this reason on its own is sufficient to prevent clear focusing of all the beam elements on a common focus area.
The problem on which the present invention is based is to create an arrangement and an apparatus of the type mentioned initially which allow a light beam to be focused better after passing through the apparatus.